The presence of supplementary intervertebral articulations termed "xenarthrales" in the posterior dorsal vertebrae has been considered perhaps the most important diagnostic feature of the mammalian order Xenarthra. Xenarthrales are poorly understood, however, and substantial confusion exists in the literature over which facets are supplementary and which are not. Furthermore, much of the variation that exists in these joints, both within taxa and among the various xenarthran lineages,... Topics: Xenarthra -- Morphology, Vertebrae
Simosaurus gaillardoti H.v. Meyer, 1842, is recognized as the only species of its genus. An amended diagnosis of the genus is given here. Simosaurus mougeoti H.v. Meyer, 1842, is a lower jaw of Nothosaurus; Simosaurus guilielmi H.v. Meyer, 1847-1855, is a junior synonym of Simosaurus gaillardoti. The skeletal morphology of Simosaurus is redescribed in detail and compared to that of other stem-group (non plesio- and pliosaur) Sauropterygia (including Placodus). Ninety-four skeletal characters... Topics: Sauropterygia -- Phylogeny, Simosaurus gaillardoti -- Morphology
byZangerl, Rainer, 1912-; Hansen, Michael C. joint author; Winter, H. Frank. joint author
The microscopic anatomy of the teeth in 9 genera and 23 species of the Paleozoic elasmobranch order Petalodontida was examined in numerous thin sections. With two exceptions, the crowns of these teeth are covered with a highly characteristic, compound tissue, which Moy-Thomas called "tubular dentine" and for which the term "orthotrabeculine" is here proposed. Orthotrabeculine consists of a hypermineralized homologue of modern shark orthodentine and peritubular trabeculine... Topics: Condrichthyes, Fossil, Teeth -- Morphology, Petalodontida -- Anatomy
byLin, Kebang; Field Museum of Natural History; Rieppel, Olivier
Keichousaurus hui Young, 1958, from the Middle Triassic of Guizhou, China, is a small sauropterygian reptile. It has a short snout and elongated temporal openings, resembling the European pachypleurosaurid Dactylosaurus. Unlike all other stem-group eosauropterygians, the parietal foramen is displaced anteriorly. The neck is long and flexible. The body is rigid and the bones pachyostotic. There are two or three sacral vertebrae. There is distinct sexual dimorphism, as in Alpine... Topics: Keichousaurus hui -- Morphology, Keichousaurus hui -- Development, Sauropyerygia -- Morphology,...
byRieppel, Olivier; Zaher, Hussam joint author Depto. de Zoologia, Instituto de Biociencias, Universidade de Sao Paulo, Brazil
A review of the morphology of the lower jaw in varanoid squamates, including mosasaurs, and basal snakes (scolecophidians, anilioids, basal macrostomatans) reveals a greater degree of variability in the differentiation of the intramandibular joint than had previously been recorded. In particular, the mandibular joint of mosasauroid squamates and snakes differs fundamentally. In mosasaurs, the dentary is primarily suspended from the prearticular and the posteriorly concave splenial receives the... Topics: Squamata -- Morphology, Squamata -- Evolution, Snakes -- Evolution, Pachyrhachis problematicus --...